Bandages can be formed from a variety of different fabrics including inter alia knitted fabrics made using a knitting or crocheting process, woven fabrics, non woven fabrics and fabrics made using an “air jet” weaving process.
Knitted bandages are made from lengths of knitted fabric that are subsequently processed by steaming and drying.
The knitted fabric is produced using a knitting machine having a knitting head that includes a number of needles depending on the width of the fabric. The knitting head knits together yarns of material to form a fabric that includes warp yarns running longitudinally along the length of the fabric and weft yarns that also run generally longitudinally along the length of the fabric but which also meander transversely across the width of the fabric across two or more of the warp yarns. This is in contrast to woven fabrics where the weft yarns normally run transversely across the full width of the fabric. The meandering arrangement of the weft yarns means that the knitted fabric has the ability to stretch in the transverse direction without the need to make the weft yarns from a material having any degree of elasticity.
The yarns can be made of any suitable material and have any size or weight per unit length (sometimes referred to as the count, denier or tex) depending on the desired properties of the finished knitted bandage. Examples of knitted fabrics are set out in Table 1 below.
TABLE 1Warp yarnsWeft yarnsExample(Number of(Number ofNumberMaterialends/cm)CountMaterialends/cm)Count1nylon1.8 +/− 10%2/78/24viscose3.7 +/−10%30s(polyamide)(cellulose)viscose1.7 +/− 10%30s(cellulose)2elastomeric3.0 +/− 10%viscose5.5 +/− 10%24syarn(cellulose)viscose5.9 +/− 10%24s(cellulose)3elastomeric yarn2.9 +/− 10%viscose5.5 +/− 10%24s(cellulose)Viscose5.6 +/− 10%24s(cellulose)Nylon0.1 +/− 10%2/78/20(polyamide)
The knitted fabric is usually gathered and stored as a roll and then subsequently processed using the apparatus shown schematically in FIG. 1.
The length of knitted fabric 2 is fed from a roll 4 over a roller 6 and between a pair of input feed rollers 8 operating at a given rotational speed. The input feed rollers 8 move the length of knitted fabric into a steaming chamber 10. The steaming chamber 10 contains a reservoir 12 that is supplied with softened water through a water inlet pipe 14. A heating element (not shown) is used to heat the water in the reservoir 12 and keeps it at a rolling boil. The length of knitted fabric 2 moves through the steaming chamber 10 above the reservoir 12 where it is exposed to the steam coming from the surface of the boiling water. The exposure to the steam causes any nylon (polyamide) warp yarns and/or any elastomeric warp yarns in the knitted fabric to shrink slightly in the longitudinal direction. This is sometimes referred to as the “relaxation step” because the warp yarns are placed in tension when they are supplied to the knitting head and the exposure to the steam allows the knitted fabric to relax and shrink back to a state where the warp yarns can provide some stretch or elasticity in the finished knitted bandage. The speed of rotation of the input feed rollers 8 is selected so that the travel time of the knitted fabric through the steaming chamber 10 (in other words the time taken for one part of the length of knitted fabric to pass through the steaming chamber 10 from one side to the other) is such that the nylon (polyamide) and/or elastomeric warp yarns are allowed to relax sufficiently for the finished knitted bandage to have the desired amount of stretch or elasticity.
At the output end of the steaming chamber 10, the length of knitted fabric passes over an intermediate feed roller 16 which is optionally driven and into a drying chamber 18. The purpose of the drying chamber 18 is to remove the moisture that is absorbed by the knitted fabric during the steaming process.
Air is supplied though an air inlet pipe 20 before being heated by a heater unit (not shown) and fed into the drying chamber 18. The heater unit has three separate heater elements (not shown) and the temperature of the air inside the drying chamber 18 is determined by switching on one, two or all three of the heater elements. The amount of air that is supplied through the air inlet pipe 20 and into the interior of the drying chamber 18 can be controlled using a vent that can be opened or closed to a specified degree of angle. Outlet vanes can be provided to make sure the hot air is evenly distributed through the inside of the drying chamber 18.
Typical processing parameters for Examples 1 and 2 are set out in Table 2 below. However, the exact temperature inside the drying chamber 18 and the travel times of the length of knitted fabric through the steaming and drying chambers will depend on the particular knitted fabric and on the desired properties of the finished knitted bandage.
TABLE 2Total travel timeTravel timethrough steamingthroughTemperatureTemperatureand dryingdryingin steamingin dryingExamplechamberschamberchamberchamberNumber(seconds)(seconds)(° C.)(° C.)17.5 to 8.54.8 to 5.88668 (1 heaterelement;air intakepipe vent 75°open)24.5 to 6.02.9 to 4.08668 (1 heaterelement;air intakepipe vent 75°open)
A pair of output feed rollers 22 are positioned at the output end of the drying chamber 18 and operate at a given rotational speed. As shown in FIG. 1, there is no tension in the length of knitted fabric 2 as it passes through the steaming chamber 10 and the drying chamber 18 so that any shrinkage or relaxation of the knitted fabric in the steaming chamber can be easily accommodated. This lack of tension in the length of knitted fabric 2 is maintained by running the output feed rollers 22 at a rotational speed that is slightly less than the rotation speed of the input feed rollers 8.
The output feed rollers 22 move the length of knitted fabric into a collecting trough 24 before it is taken up and fed into a rolling machine 26. The rolling machine 26 rolls the processed knitted fabric and cuts it into shorter lengths so that the finished knitted bandages can be packaged. A suitable rolling system would consist of:                (i) Type TAD shrinking and finishing machine        (ii) Type 7.10 automatic winding rolling machine        
These are made and supplied by IVF Technology AG, CH-8212, Neuhausen, Switzerland.
The input, intermediate and output feed rollers 8, 16 and 22 can be stopped and started manually by an operator or automatically with the rolling machine, for example. During the period of time when the input, intermediate and output feed rollers 8, 16 and 22 are not being driven and the length of knitted fabric 2 is stationary, the drying chamber 18 can be opened or vented to allow the hot air to escape so that the length of the knitted fabric within the drying chamber is not burnt or scorched.
The advantages of giving antibacterial and antimicrobial properties to fabrics are known. For example, WO 2005/038122 describes a method of preparing a fabric containing silver having antibacterial properties. The method includes the following steps of (i) preparing a solution containing H4Ag2O6, (ii) impregnating, leaching, spraying or coating the fabric with the solution, and (iii) drying the wet fabric. When tested with a cotton unwoven textile the amount of silver in the dried fabric was found to vary between 2.3 and 86.8 μg/cm2. Antibacterial reduction of Staphylococcus aureus was shown to vary between 97.71% and 100.00% depending on the particular sample used.